Unlike the other recent Blue-throated, this bird seems to have an all-blue throat. Rubeculoides is the only subspecies of Blue-throated to have an all-blue throat, but should be brighter orange on the breast than this bird (with the orange more clearly defined). Chinese Blue (glaucicomans) and (I think) Blue-throated dialilaema would have a much wider orange wedge, easily visible from this angle. The orange wedge on Blue-throated klossi can be difficult to see, but I think would still be visible at this angle.
Based on this photo, I would consider this most likely to be Hainan Blue. Perhaps a first-winter male still with some retained juvenile breast feathers? Do you have any more photos to confirm the pattern of blue on the breast/throat?
